Hide part of object during animation
Use some transparent object and make the boolean difference with the door.

Modifier setup on right below:





Alternatively, if for instance the boolean fails, you can modify the door material so that everything above an empty is set transparent:



The node setting compares the empty position (object texture coordinates, so one location) to the correspondant location on the object surface (also one location). If the Z part of these locations are showing that the door is upper the empty, alpha is set to zero.